I've noticed that Defragging the drives and Defragging free space are 2 separate defrag operations. Which is the best way to fully optimize my drive?
Defrag drive -> Defrag free space -> Boot time Defrag?
It'll be great if Piriform is able to integrate the defrag of free space into the regular drive defrags.
Which is the best way to fully optimize my drive?
The best way is each user's opinion. My drives are partitioned, so I defrag a partition once, thereafter defrag only the files.
Tick ☑ filename 
and click Defrag Checked. Fastest results.
Boot-time defrag fixes only some blocked files.
I once did a free space defrag and didn't notice any results, so don't run it anymore.
Keep in mind that, right now, Defrag Freespace alone will create more fragmentation.
+1 to what Kroozer said.
If you have the inclination and time try Analyze and Defrag afterwards. It will combine both normal defragging + Defrag Freespace (doing it okay. Filling most gaps) but it CAN BE UTTERLY SLOW...
What about Defrag Freespace (Allow Fragmentation)? Shouldn't it be the other way round? Would using CCleaner's wiping of free space eliminate free space fragmentation?
After analysing, there's only the defrag option. I don't see an option to Defrag free space.
Also, +1 to Defrag checked files. I've tried it myself, you get to defrag exactly what's fragmented, since I noticed that Defragging an entire partition doesn't do a thoroughly clean job.
Thanks for the replies too!
After analysing, there's only the defrag option. I don't see an option to Defrag free space.
Analyze ► Action ➢ Advanced ➢ Defrag Freespace options 
Thanks kroozer for the reply.
If you have the inclination and time try Analyze and Defrag afterwards. It will combine both normal defragging + Defrag Freespace (doing it okay. Filling most gaps) but it CAN BE UTTERLY SLOW...
What I meant was, according to pusher, if you analyze and defrag afterwards, you get both normal defragging and defrag freespace? How is it that this defrag afterwards has both normal and free space defrag?
In the pulldown menu there are two modes: Defrag and Quick Defrag. The regular Defrag mode will defrag everything and consolidate free space too.
The Quick Defrag mode will defrag most files and will not attempt any free space consolidation.